Exhaust system for diesel vehicles

ABSTRACT

An exhaust system for diesel vehicles is described, which includes at least one metering device for introducing and metering a pollutant-reducing medium into an exhaust gas flowing through a flow pipe of an exhaust tract of an internal combustion engine, in particular for the purpose of introducing a reduction agent and/or a reduction agent precursor, for example urea and/or an aqueous urea solution, the exhaust tract having at least one flexible flange connection.

This claims the benefit of German Patent Application DE 10 2013 016 235,filed Oct. 1, 2013 and hereby incorporated by reference herein.

The present invention relates to an exhaust system for diesel vehicles,which includes a flexible flange. Flanges are used in a method forconnecting pipe sections or air ducts to each other tightly yetdetachably. The contact pressure of the ring-shaped sealing surfaces onthe intermediate seal is crucial for the tightness. The contact pressureis applied with the aid of screws which are inserted into the flangefaces through bores. These flanges are generally welded to the pipe.They belong to the pipeline parts or fittings. For example, flanges ofthis type are cast onto fittings and measuring devices. For example,steel flanges, cast iron flanges, flanges made of copper alloys andflanges made of aluminum alloys are known. Flanges made of high gradesteel or carbon steel types are also known.

BACKGROUND

The word flange means “to project from a surface.” Pipeline flangesproject from a pipeline. However, another explanation is that atradesman is able to flange something onto a wall. The term also refersto flanges (chords) which form the upper and lower ends of a steel Hbeam (previously: double T beam).

There are different types of flanges, which are used for different areasof application. For example, flanges may be welded or screwed onto thepipe. Some types of flanges offer better stability, e.g., little facedeformation under high screw forces to meet special tightnessrequirements.

Welding neck flanges are flanges with a neck for welding onto a pipe,for example. They are preformed from a steel blank by forging andsubsequently finished by turning and drilling. Larger flanges are alsobent into rings from profile steels and then welded. This type of flangeis particularly structurally stable and is also used under highpressures.

Slip-on weld flanges with a neck are pushed onto the pipe and thenwelded to the pipe. The term slip-on flange is used under the ANSIstandard.

Smooth flanges are pushed onto the pipe and then welded to the pipe.They are usually manufactured from a metal sheet. Larger flanges arealso bent into rings from flat steel and then welded.

Blind flanges have no central bore and are used for sealing, forexample, additional connecting pieces on pressure tanks or the ends ofpipelines.

Threaded flanges have an inner thread into which the pipe is screwed,instead of a neck for welding.

Loose flanges are pushed loosely onto the pipe. The actual fastening tothe pipe is handled by the welding neck ring or welding neck collar tobe welded on. They are also used for integrally molded flanges. Thisdesign is used if the position of the pitch circle of the mating flangecannot be defined until final assembly.

Block flanges include a forged or a cast block. The associated screwholes have an inner thread. Flanges of this type are primarily weldedonto pressure tanks as pipe sockets and used to attach inspectionglasses.

Vessel flanges have the same function as normal flanges but arepreferably used on boilers, pressure tanks and similar vessels. They cantherefore have different dimensions of the flange face thickness, e.g.,in the case of cast housings.

SAE flanges are used in various designs in oil hydraulics. These flangefittings are also known as CAT flanges, since they were developed byCaterpillar in the United States. SAE flanges are divided into pressurelevels of 3,000, 6,000 and 9,000 PSI.

Vacuum flanges are used for the detachable connection of vacuumchambers. They are available as small flanges, clamp flanges and CFflanges.

In exhaust systems having SCR technology, the pipe connections aregenerally designed as screw connections or welded connections aftermetering of the reduction agent (AdBlue/DEF/AUS32). These connectionshave the disadvantage that the torsion of the two pipe sides withrespect to each other is not possible at all (welded connection) or ispossible only in keeping with the flange pattern (screw connection).

Known 6-hole flanges permit a torsion of an SCR catalytic converter withrespect to the mixing line in 60° increments. This is unsuitable whenthere is limited installation space.

SUMMARY OF THE INVENTION

It is an object of the present invention to avoid the aforementioneddisadvantages.

The present invention provides an exhaust system for diesel vehicles,which includes at least one metering device for introducing and meteringa pollutant-reducing medium into an exhaust gas flowing through a flowpipe of an exhaust tract of an internal combustion engine, in particularfor the purpose of introducing a reduction agent and/or a reductionagent precursor, for example urea and/or an aqueous urea solution, theexhaust tract having at least one flexible flange connection.

It is advantageous that the flange torsion may occur flexibly, the axialcompression of the seal taking place in such a way that an optimumcontact pressure is implemented as well as a sealing of the systemagainst AdBlue and exhaust gas.

A further advantage in the case of loose flanges and blind flangesexists if, instead of the standard flange face thickness, a facethickness which meets the particular requirements, i.e., a reduced facethickness, is used. A uniform force distribution/precisely definedintroduction of force on the sealing area is possible.

The flexible flange connection is suitable for any type of exhaustsystem and not only for SCR applications.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional important features and advantages are derived from thesubclaims, from the drawings and from the following description of onepreferred exemplary embodiment on the basis of the drawings.

FIG. 1 shows an exploded drawing of a screw flange;

FIG. 2 shows a top view and a side view of the screw flange from FIG. 1;

FIG. 3 shows sectional representation A-A of the screw flange from FIG.2;

FIG. 4 shows an exhaust system of an internal combustion engine.

DETAILED DESCRIPTION

The present invention illustrates a screw connection, which facilitatesthe adjustment of the two pipes with respect to each other prior totightening the screws, in any arbitrary angular position and thusindependently of the hole pattern of the screw flange.

Flexible flange connection 9 (FIG. 4) is “AdBlue-tight”; tight againstDEF, AUS 32 according to ISO 22241, and tight against all common fuelsand their condensates as well as tight against all exhaust gases frominternal combustion engines.

The flange connection illustrated in FIG. 1 is a screw connectionbetween two pipes 1, 8. One pipe side 8 is fixedly welded to a flange orflange face 4. The mating side permits the free torsion of pipe 1, dueto a loose flange 2, and thus a variable adjustment independently of thehole pattern of the flange. Following the desired adjustment of the twopipes 1, 8 with respect to each other, flanges 2, 4 or flange faces arescrewed to each other. Seal 3 is pressed between the flanged frontsurface of pipe 1 and mating flange 4 with the aid of screws 5, spacersleeves 6 and nuts 7.

FIG. 2 shows a top view and a side view of the screw flange from FIG. 1.The flange connection is a screw connection between two pipes 1 and 8.One pipe side 8 is fixedly welded to a flange or flange face 4. Themating side permits the free torsion of pipe 1, due to a loose flange 2,and thus a variable adjustment independently of the hole pattern of theflange. Following the desired adjustment of the two pipes 1, 8 withrespect to each other, flanges 2, 4 or flange faces are screwed to eachother. Seal 3 described in FIG. 1 is pressed between the flanged frontsurface of pipe 1 and mating flange 4 with the aid of screws 5, spacersleeves 6 and nuts 7.

A sectional view along section line A-A of the screw flange from FIG. 2is shown in FIG. 3.

The described flange connection is a screw connection between two pipes1 and 8. Pipe side 8 is fixedly welded to a flange or flange face 4. Themating side permits the free torsion of pipe 1, due to a loose flange 2,and thus a variable adjustment independently of the hole pattern of theflange. Following the desired adjustment of the two pipes 1 and 8 withrespect to each other, flanges 2, 4 or flange faces are screwed to eachother. Seal 3 is pressed between the flanged front surface of pipe 1 andmating flange 4 with the aid of screws 5, spacer sleeves 6 and nuts 7.

FIG. 4 shows a schematic representation of an exhaust system of aninternal combustion engine, which includes an engine 14 from which anexhaust tract 13 extends in the flow direction of the exhaust gas ofengine 14. Following exhaust tract 13, a pipe 1, which is used as amixing line for exhaust gas and urea metering device 11 integrated intopipe 1 extends in the flow direction of the exhaust gas of engine 14.Exhaust tract 13 and pipe 1 are connected gas-tight with the aid of aflange 12. An SCR catalytic converter is situated at the end—in the flowdirection of the exhaust gas of engine 14—of pipe 1 used as the mixingline. Pipe 1 and SCR catalytic converter 10 are connected to each otherwith the aid of gas-tight and liquid-tight flexible flange connection 9,which is illustrated in FIGS. 1, 2 and 3.

Embodiments of the flange in accordance with the present invention maybe used, in principle, for all exhaust gas-tight or liquid-tight pipingin exhaust systems or gas-conducting, i.e., hot gas-conducting,piping/pipe screw connections.

In particular, and in the case implemented herein, embodiments of theflange in accordance with the present invention are used to seal theexhaust gas piping of an SCR catalytic converter against the AdBluereduction agent (AUS 32; DEF) in the exhaust gas.

LIST OF REFERENCE NUMERALS

1 pipe (flanged on the outlet side)/mixing line

2 Flange (loose)

3 Seal (AdBlue-resistant)

4 Flange (equivalent part to reference numeral 2)

5 Screws

6 Spacer sleeve

7 Nut

8 pipe (welded onto flange reference numeral 7 [sic; 4])

9 Flexible flange connection

10 SCR catalytic converter

11 Metering device/urea metering

12 Flange

13 Exhaust tract

14 Engine

What is claimed is:
 1. An exhaust system for diesel vehicles comprising:an exhaust tract of an internal combustion engine including a flow pipe;and at least one metering device for introducing and metering apollutant-reducing medium into an exhaust gas flowing through the flowpipe of the exhaust tract, the exhaust tract having at least oneflexible flange connection.
 2. The exhaust system for diesel vehicles asrecited in claim 1 further comprising a SCR catalytic converter, theflexible flange connection being situated upstream from the SCRcatalytic converter.
 3. The exhaust system for diesel vehicles asrecited in claim 1 wherein the flow pipe is a mixing line for thepollutant-reducing medium and the exhaust gas, the flexible flangeconnection being situated in the area of the mixing line and in a flowdirection of the exhaust gas.
 4. The exhaust system for diesel vehiclesas recited in claim 1 wherein the flexible flange connection has atleast two flanges.
 5. The exhaust system for diesel vehicles as recitedin claim 1 wherein the flexible flange connection has at least one looseflange.
 6. The exhaust system for diesel vehicles as recited in claim 1wherein the flexible flange connection has at least one flanged pipe ata flow-side outlet side.
 7. The exhaust system for diesel vehicles asrecited in claim 1 wherein the flexible flange connection includes aflange and at least one pipe attached to the flange.
 8. The exhaustsystem for diesel vehicles as recited claim 1 wherein the at least onemetering device introduces at least one of a reduction agent and areduction agent precursor.
 9. The exhaust system for diesel vehicles asrecited claim 8 wherein the at least one metering device introduces atleast one of urea and an aqueous urea solution.